Overview

A Tumor or tumour (via Old French tumour from Latintumor "swelling")[1] originally meant an abnormal swelling of the flesh. In contemporary English, tumor has evolved to become synonymous with neoplasia[2], all other forms being called swelling[3]. This tendency has also become common in medical literature. The noun tumefaction, derived from the adjective tumefied, is the current medical term for non-neoplastic tumors [4].

Inflammation, by far the most common cause; tumor is one of the classic signs of inflammation.[5] The lump following a blow on the head is a typical example. Infection is another common cause of inflammation.

Edema, the accumulation of an excessive amount of fluid in the tissues, either with or without inflammation.

Other forms of swelling are part of the normal functions of the body and may or may not be included as causes of tumor. Examples include enlargement of the uterus in pregnancy and erection of the penis.